(CNN) -- At least seven people were killed and another 18 were missing early Sunday after a nursing home caught fire in northwestern Russia, state media reported.

Firefighters in the republic of Komi spent several hours fighting the blaze.

Irina Valentinova, a spokeswoman with the Russian Ministry of Emergency Services, said that details about the fire were still emerging early Sunday and that the government does not think the current death toll will be final.

Russian media were reporting that authorities were slow to report the fire, making it more difficult for firefighters to battle the blaze in a building engulfed in flames when they arrived.

Lubov Terenteva of the emergency ministry in Komi said that by early Sunday, the fire was out and rescue workers were clearing the scene and searching for survivors.

Authorities did not know what caused the fire, Terenteva said.

President Dmitry Medvedev ordered the Russian prosecutor general's office to conduct an investigation of the fire.

The order comes after reports show that there have been frequent fires at Russian hospitals, schools and other state-run facilities. Many Russians blame the fires on official negligence and violations of fire safety rules.